The present invention relates to a steam box, which includes an elongated steam-distribution chamber, regulator chambers set in a row next to this and covered on one side with a continuous perforated screen, and operating devices to distribute the steam from the distribution chamber to each regulator chamber, and which steam box is intended to feed steam through the perforated screen to the web, to heat it according to the desired profile.
U.S. Pat. No. 5,711,087 (Pazdera) discloses a heating device for heating a web. Steam or hot air is fed to the web from a elongated chamber through a perforated screen conforming to the shape of the web. The screen easily dirties in use and must be cleaned. To facilitate this cleaning, the perforated screen is arranged to be detachable, in such a way that both of its long sides are attached to the frame of the apparatus by means of clip members.
The width of the regulator chambers of modern profiling steam boxes can be as little as 60mm, which permits a precise heating profile over the width of the web. A relatively common construction is one, in which each regulator chamber is equipped with a condensation water removal muff pipe, through which the water flows to the casing space, from which it is removed separately. One end of the muff is normally closed with a plug, but during maintenance the plug is removed, opening the condensing water channel through the muff. This is quite laborious, while it is impossible to gain access to the whole regulator chamber. Naturally, the perforated screen (diffusion plate) can be cleaned from outside using a water jet, but even this operation will carry fibers into the regulator chambers.
The construction in the aforesaid U.S. publication permits easy access to the regulator chambers, but the removal and installation of the perforated screen has turned out to be difficult. Its length corresponds essentially to the width of the web, making it quite heavy to handle.
The present invention provides a steam box, which can be easily cleaned.
More specifically, the steam box includes an elongated steam-distribution chamber, regulator chambers set in a row next to the elongated steam-distribution chamber and covered on one side with a continuous perforated screen. Operating devices are operable to distribute the steam from the distribution chamber to each regulator chamber. The steam box feeds steam through the perforated screen to a web, to heat it according to a desired profile. The steam box is characterized in that the the perforated plate is secured along one long edge to hinge members and along the opposite side to a locking member and arranged so that it can be opened to permit access to the regulator chambers.
The regulator chambers are formed in a unified elongated space by separating them from one another by means of partition walls, and the perforated screen is arranged to press directly against these partition walls.
A unified auxiliary distribution chamber on the other side of the distribution chamber equipped with another heat-distributing perforated screen and in which the distribution chamber and the auxiliary distribution chamber are covered with a unified plate, the other perforated screen being part of this unified plate.
The hinge members are installed on the outer edge side of the regulator chambers and the locking members on the distribution chamber side. The locking members comprise an axle secured rotatably to the inside of the free edge of the perforated screen, with indentations formed at regular intervals along it, and stops extending to the axle and set at corresponding intervals along the edge of the regulator chambers. The axle is arranged to be able to pass the stops at those stops that are in the indentations and to lock against the stops that have been turned to the bottom of the indentations.
The entire web-side edge of the steam box is arranged to be opened as one or more parts, with each part being secured to the aforesaid hinge members along one long edge of the steam box, the locking members being on the opposite edge.
The perforated screen, i.e. diffusion plate, which is supported on hinges, can be in one or more parts, together covering the entire width of the web. The hinges permit the screen to be opened safely and lightly by one person.